DSL (Digital Subscriber Line, digital subscriber line) is a technology for implementing high-speed data transmission over a phone twisted-pair cable.
When a user performs broadband access through a DSL, the user needs to activate the DSL first. During the activation of the DSL, to eliminate crosstalk among DSL lines of different users, it is necessary to perform vectoring (Vectoring) training.
In the existing VDSL2 (Very-high-bit-rate Digital Subscriber line 2, very-high-bit-rate digital subscriber line 2) standard, that is, G.993.2, the time taken for performing vectoring training once is 25.6 seconds, while the time taken for performing DSL activation once is required to be 40 seconds. Therefore, the time for performing vectoring training once takes up 64% of the total DSL activation time, so that the DSL activation time is excessively long, thereby severely affecting the speed for a user to go online and resulting in poor user experience.
An existing method for decreasing the length of an orthogonal sequence borne in a sync frame (sync frame) can shorten the activation time of a user. However, the method may cause a noise problem, for example, crosstalk noise cannot be canceled or additive white Gaussion noise (Additive White Gaussion Noise, AWGN) cannot be effectively eliminated.